The invention is based on a fuel injection pump as defined hereinafter.
Before fuel injection pumps of this kind, embodied as multi-cylinder pumps having a series of pump elements, are put into operation, an exact association of the individual control slides with respect to the various control openings must be made, since during pump operation the individual control slides are displaced simultaneously and in common by the rotary shaft, for variation of the instant of injection or the injection quantity. Even slight errors in this association, that is, differences in the desired control points of the various control slides with respect to one another, can lead to considerable errors in the control of injection onset or injection quantity, which in turn can for instance lead to rough engine operation or excessively noisy combustion.
These deviations in the association of the individual control slides with respect to one another are due to tolerances originating in the machining or assembly process, or in the pump drive shaft, and the deviations can be superimposed on one another. These deviations must be eliminated, by positioning the control slides uniformly with respect to the control openings before the pump is put into operation.
In a known fuel injection pump of this generic type (German Offenlegungsschrift 35 22 414), the driver tang is secured to a clamping ring encompassing the rotary shaft; once the clamping ring is loosened, the position of the tang, and thus the axial position of the control slide relative to the rotational position of the rotary shaft, can be varied. Not only does the adjusted position between the driver arm and rotary shaft shift on its own, given the heavy loads and constant jarring that a fuel injection pump undergoes, but adjustment is also a relatively labor-intensive operation because it requires making a direct comparison between the various pump elements; moreover, when the clamping rings are adjusted on the rotary shaft, they may exert torque upon the shaft that can lead to further errors in adjustment A further disadvantage is that the adjustment can be done only in the installed condition; only then can the individual association between the change in rotational position of the rotary shaft and the clamping ring, on the one hand, and the change in axial position of the control slide, on the other, be reliably performed, which has the disadvantage that for adjustment, an intervention into the suction chamber must be made when it is at feed pump pressure.
In another known fuel injection pump of this generic type (German Offenlegungsschrift 35 40 052), the driver arm is disposed eccentrically on a spindle that penetrates the rotary shaft radially and is clamped to it with a tightening nut. When the spindle is rotated, which is done by engaging a slit with a screwdriver after the tightening nut is loosened, the driver arm is adjusted as a function of its eccentricity with respect to the axial position of the control slide. In this known apparatus as well, the fact that the adjustment, once made, loosens on its own again is all the more disadvantageous, the smaller the friction faces involved in the tightening of the spindle. Also, once again this adjustment can be performed only with the rotary shaft in its installed state, and once again the suction chamber, which is under pressure, must be opened up.
In yet another known fuel injection pump of this generic type (European patent application 0181 402), a fork-like device having a gripper insert acts as the driver element; it is connected to the rotary shaft either with a tubular clamp, in which case the rotary shaft is round in cross section, or via a bolt, disposed on the face end of the forked lever facing the rotary shaft, which in that case has a polygonal cross section. Although in the first case adjustment is relatively simply done by rotating the "tubular clamp" on the rotary shaft, there is still the danger that jarring in such systems easily loosens the clamp tension and can cause the control slide association to change, possibly in the direction of increasing fuel quantity, which will cause the engine to race. The second case is extremely unfavorable in terms of force transmission, because the area of contact, between the lever and the rotary shaft, that is operative in the longitudinal direction of the lever is relatively narrow, and moreover, as noted above, the desired adjustability is not available.